Loudspeaker system



Feb. 21, 1939. D R. HALL ET AL LOUDSPEAKER SYSTEM Filed Feb. 25, 193'? INVENTORS iv G /k/san ATTORNEY.

speaker unit.

Patented Feb. 21, 1939 PATENT OFFICE 2,147,894 LOUDSPEAKER' SYSTEM Donald R. Hall, Oakland,

and Ernest G. Danielson, San Francisco, Calif, assignors to Remler Company, Ltd., San Francisco, Calif., a corporation of California Application February 23, 1937, Serial No. 127,030

5 Claims.

This invention relates generally to loud speaker systems of the type in which one or more remote loud speaker units are connected to a central amplifier system.

In certain loud speaker systems, maintenance of the individual loud speaker units in proper operating condition is of prime importance. For example this is true of marine installations, where the individual loud speakers may be distributed over diiferent parts of the ship, and where wiring for connecting the loud speakers to the central system is subject to accidental damage. The present invention has for its object the provision of indicating means which will at all times indicate either open or short-circuited conditions of the Wiring, so that an operator may determine whether or not a particular speaker is operating properly.

Another object of the invention is to provide an indicator arrangement for a loud speoker sysof an indicator lamp of the filament type, together with an exciting current that is superposed upon the same circuit which carries the voice currents to the loud Further objects of the invention will appear from the following description in which the preferred embodiments of the invention have been set forth in detail in conjunction with the accompanying drawing' 1 Referring to the drawing:

Fig. 1 is a circuit diagram, illustrating one form of the invention.

Fig. 2 is likewise a circuit diagram, illustrating a modification of the invention.

Fig. 3 is a circuit diagram, illustrating a further modification applicable to a plurality of loud speaker units.

Fig. 4 is a diagrammatic circuit layout, showing a complete loud speaker system.

Referring first to Fig. 1, I have shown a power amplifier ID of the electron relay type, which forms a part of an amplifier system. In this instance the amplifier is of the push-pull type, making use of two amplifier tubes, together with a plate circuit transformer II. The input of amplifier l connects to some source of Voice currents, such as the output of a voltage amplifier, which in turn has its input connected to a micro- 5 phone circuit. The loud speaker unit l2 includes a conventional voice'coil 13, which is shown connected to the secondary of transformer I4.

Ordinarily the primary of transformer I4 would be directly connected to thesecondary of ;5 transformer l l, by a simple link circuit including the extended conductor lines L1 and L2. However if these lines should become open-circuited or short-circuited, the loud speaker unit l2 would fail to operate, but this condition would not be indicated in any way to the operator located at the amplifier end of the circuit.

To afford indicating means I make use of a small indicator lamp l6 of the filament type, which in this instance is connected in series with conductor L1, as illustrated. Also in series with the circuit there is a source of exciting current which in this instance is represented by a battery l1. In order to maintain the system in operative condition in the event the filament of lamp l6 becomes open-circuited, the lamp is shown shunted by a resistor l8, which has a value of resistance relatively high compared to the resitsance of the lamp.

It will be apparent that the current flow from the battery I! is determined mainly by the resistance of the connecting lines L1 and L2, the resistance values of the secondary winding of transformer II, the primary of transformer l4, and the combined resistance of resistor H3 in shunt with lamp [6. The voltage of battery I? is adjusted so that the lamp [6 is normally burned at somewhat lines L1 and L2 become opencircuited, current supply from the battery I! will be interrupted, and the lamp I6 will be extinguished. If lines L1 and L2 become short-circuited considerable resistance, including that of the primary winding of transformer I4, is removed, and lamp It is burned at a noticeably greater brilliancy. Such indications will be had irrespective of use of the amplifier, with the exception however that when the amplifier is in use and lines L1 and L2 are conducting voice currents, there will be some variation in the illumination of lamp It.

In the modification of the invention shown in Fig. 2, a shunt arrangement is provided for the indicating lamp l 6, in place of the series arrangement of Fig. 1. Thus in this case the lamp I t is connected in series with a choke inductance 2|, the direct current resistance component of which is relatively low, but which has relatively high reactance to voice frequencies. A resistor 22 is connected in series with the secondary of transformer H, and the transformer secondary plus the resistor 22, is connected in shunt with the serially connected lamp I6 and choke 2|. Resistor 22 serves to minimize flow of current from the battery I! through the secondary of transformer H, thus serving to cause a major part of the current to how through conductor lines L1 less than full brilliancy. If

former and also and L2 and the primary of transformer I4, to illuminate the lamp l6. It will be apparent that with this arrangement any open circuit in lines L1 and L2 will cause current fiow through lamp l6 to be interrupted, with the result that lamp [6 is extinguished. Short-circuiting of lines L1 and L2 causes a materially greater current fiow through lamp [6, thus causing the lamp to burn at greater than normal brilliancy.

Fig. 3 illustrates a system substantially the same as that described with respect to Fig. 2, except that in this instance a plurality of .loud speaker units I211, I21) and I20, are connected to a common amplifier II). It will be noted that signal lamps 16a, I61) and lfic 'are provided for each of the loud speaker units, and that each signal lamp is also associated with an individual resistor 22a, 22b and 220, which correspondto the resistor 22 of Fig. 2. In such a systemlthere will be a continuous indication, making it possible to immediately note an open-circuited or shortcircuited condition of any one of the circuits leading to the loud speaker units, and to determine which one of the loud speaker units-is inoperative.

Fig. 4 illustrates a complete system making useof an indicator arrangementsimilar to Fig. 1, but with a plurality of loud speaker units. A microphone or microphone circuit is represented at 8, and connects to a driver or potential amplifier 9. The output of the driver amplifier connects with the separate :power amplifiers lllato Hid inclusive, each-of which connectsto itsindividual loud speaker unit, by an arrangement such as shown in Fig. 1. The arrangement of Fig. 4 has some advantages over the system of Fig. 3, in that failure of any one power amplifier will cause failure of only one loud speaker unit, whereas failure of the power amplifier ID in Fig. 3, will make the entire system inoperative.

We claim:

1. In a loud speaker system making use of a power amplifier of voice currents having aplate transformer and also making use of a remote loud speaker unit, the loud speaker unit including a voice coil and a transformer having both sides of its secondary connected to the voice coil, a circuit serving to link the output of the amplifier to said loudspeaker unit, the circuit including the secondary of the amplifier transformer'and also including a pair of conductor lines extending from the amplifier to -the primary of the loudspeaker transformer, a source of direct current located-at the amplifier end ofthe circuit and connected in series with the conductor lines to impose a direct current component upon said circuit, said direct current component being isolated from the secondary of the loudspeaker transformer,.and an indicating lamp likewise connected to said circuit at theamplifier end of the same, and serving to indicate direct current flow through the conductor lines.

2. Ina loud speaker system making use of a power amplifier of voice currents having a plate transformer, and also making use of a remote loud speaker unit, a circuit serving to link the output of the amplifier to said loud speaker unit, said circuit including the secondary winding of said transformer and also including a pair" of conductor lines extending from the amplifier to the speaker unit, a source of energizing current connected in series with the secondary of said transwith said conductor lines, an indicator lamp of the filament type connected in series with the secondary-of said transformer at the amplifier end of said circuit, and a resistance shunting said lamp, said lamp being illuminated at a predetermined intermediate brilliancy during normal operation of the system, and being extinguished in the event the conductor lines are open-circuited, and burned at a greater brilliancy than said conductor lines are short-circuited.

-3. In a loud speaker system making use of a power amplifier of voice currents having an output transformer, and also making use of a remote loud speaker unit,

a circuit serving to link the output of the amplifier to said loud speaker unit, said circuit including :a pair of conductor lines connected at the-amplifier end to the secondary of said transformer and connected at the loud speaker end to electrical elements of a loud speaker-unit having both reactance and resistance components, a source of current connected tothe circuit at the amplifier end of the same and in series with both the secondary of the transformer and-with saidconductor line, a resistance connected in-series with the secondary of said output transformena choke inductance having relatively low value of :resistance and a relatively high reactance to-voice currents, an indicator lampof the filament type connected in series-with said choke-said lamp and said choke being connected in shunt with the secondary of the output transformer and said resistance, whereby said lamp serves to indicate both opencircuited or-closed-circuited conditions of said conductor line.

4. In a loud speaker system of the character described'making use of a power amplifier of voicecurrents having a plate transformer, and also making use of a remote loud speaker unit including a voice coil and a transformer having its secondary connected to the voice coil, a conductive circuit-serving to link the output of the amplifiento said loud speaker unit, said circuit including a pair of :conductor lines extending fromthe amplifier to the speaker unit, the amplifier end of the conductor lines being connected to the secondary of the amplifier transformer and the loud speaker ends of theconductor lines being connected to the primary of the loud speaker unit transformena source of current serially connected with said circuit at the amplifier end of the same, and indicating means associated with the amplifier end of said circuit and serving to indicate either sho-rt-circuited or open-circuited condition of said conductor line, said indicating means-including a signal lamp of the filament type.

-5. In a loudspeaker system of the character described, making use of 'a power amplifier of voice currents having a plate transformer and also-making use of a plurality of remote loud speaker units, each including a voice coil, and a transformer having its secondary. connected to the voice coil, a plurality of circuits serving to link the output of the amplifier to said loudspeaker unit, said circuits including a plurality of conductor lines connected to the secondary of ,the amplifier transformer, the loud-speaker ends of the conductor lines being connected to the primaries of the loudspeaker transformers, thereby forming a plurality of separate current distribution circuits all connected to the secondary of the amplifier transformer, a source of direct current'serially connected with one side of the secondary of the amplifier transformer, whereby direct current components are imposed upon all of said circuits, a plurality of signal lamps of the filament type located at the amplier end of said conductor, a plurality of choke inductances each having a relatively low value of resistance and a relatively high reactance to voice currents, each of said chokes being serially connected with an associated filament lamp, a plurality of resistors connected in series with the other side of said amplifier transformer secondary and said distribution circuit, each lamp and its associated choke being connected in shunt across the secondary of the amplifier transformer and said resistances, whereby each lamp serves to indicate both open circuited or closed. circuited conditions of its associated distributing circuit.

DONALD R. HALL. ERNEST G. DANIELSON. 

